gobject-Generic-values.html [plain text]
<html><head><meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"><title>Generic Values</title><meta name="generator" content="DocBook XSL Stylesheets V1.65.1"><link rel="home" href="index.html" title="GObject Reference Manual"><link rel="up" href="rn01.html" title="API Reference"><link rel="previous" href="gobject-Boxed-Types.html" title="GBoxed"><link rel="next" href="gobject-Standard-Parameter-and-Value-Types.html" title="Parameters and Values"><link rel="preface" href="pr01.html" title="Introduction"><link rel="reference" href="rn01.html" title="API Reference"><link rel="refentry" href="gobject-Type-Information.html" title="GType"><link rel="refentry" href="GTypePlugin.html" title="GTypePlugin"><link rel="refentry" href="GTypeModule.html" title="GTypeModule"><link rel="refentry" href="gobject-The-Base-Object-Type.html" title="GObject"><link rel="refentry" href="gobject-Enumeration-and-Flag-Types.html" title="Enums and Flags"><link rel="refentry" href="gobject-Boxed-Types.html" title="GBoxed"><link rel="refentry" href="gobject-Generic-values.html" title="Generic Values"><link rel="refentry" href="gobject-Standard-Parameter-and-Value-Types.html" title="Parameters and Values"><link rel="refentry" href="gobject-Varargs-Value-Collection.html" title="Varargs Value Collection"><link rel="refentry" href="gobject-GParamSpec.html" title="GParamSpec"><link rel="refentry" href="gobject-Signals.html" title="Signals"><link rel="refentry" href="gobject-Closures.html" title="Closures"><link rel="refentry" href="gobject-Value-arrays.html" title="Value arrays"><link rel="reference" href="rn02.html" title="Tools Reference"><link rel="refentry" href="glib-mkenums.html" title="glib-mkenums"><link rel="refentry" href="glib-genmarshal.html" title="glib-genmarshal"><link rel="refentry" href="gobject-query.html" title="gobject-query"><link rel="index" href="ix01.html" title="Index"><link rel="section" href="gobject-Generic-values.html#id2812129" title="Description"><link rel="section" href="gobject-Generic-values.html#id2812231" title="Details"><link rel="section" href="gobject-Generic-values.html#id2814174" title="See Also"><meta name="generator" content="GTK-Doc V1.2 (XML mode)"><link rel="stylesheet" href="style.css" type="text/css"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><table class="navigation" width="100%" summary="Navigation header" cellpadding="2" cellspacing="2"><tr valign="middle"><td><a accesskey="p" href="gobject-Boxed-Types.html"><img src="left.png" width="24" height="24" border="0" alt="Prev"></a></td><td><a accesskey="u" href="rn01.html"><img src="up.png" width="24" height="24" border="0" alt="Up"></a></td><td><a accesskey="h" href="index.html"><img src="home.png" width="24" height="24" border="0" alt="Home"></a></td><th width="100%" align="center">GObject Reference Manual</th><td><a accesskey="n" href="gobject-Standard-Parameter-and-Value-Types.html"><img src="right.png" width="24" height="24" border="0" alt="Next"></a></td></tr></table><div class="refentry" lang="en"><a name="gobject-Generic-values"></a><div class="titlepage"><div></div><div></div></div><div class="refnamediv"><h2><span class="refentrytitle">Generic Values</span></h2><p>Generic Values — A polymorphic type that can hold values of any other type</p></div><div class="refsynopsisdiv"><h2>Synopsis</h2><pre class="synopsis">
#include <glib-object.h>
#define <a href="gobject-Generic-values.html#G-VALUE-HOLDS-CAPS">G_VALUE_HOLDS</a> (value,type)
#define <a href="gobject-Generic-values.html#G-VALUE-TYPE-CAPS">G_VALUE_TYPE</a> (value)
#define <a href="gobject-Generic-values.html#G-VALUE-TYPE-NAME-CAPS">G_VALUE_TYPE_NAME</a> (value)
#define <a href="gobject-Generic-values.html#G-TYPE-IS-VALUE-CAPS">G_TYPE_IS_VALUE</a> (type)
#define <a href="gobject-Generic-values.html#G-TYPE-IS-VALUE-ABSTRACT-CAPS">G_TYPE_IS_VALUE_ABSTRACT</a> (type)
#define <a href="gobject-Generic-values.html#G-IS-VALUE-CAPS">G_IS_VALUE</a> (value)
struct <a href="gobject-Generic-values.html#GValue">GValue</a>;
#define <a href="gobject-Generic-values.html#G-TYPE-VALUE-CAPS">G_TYPE_VALUE</a>
#define <a href="gobject-Generic-values.html#G-TYPE-VALUE-ARRAY-CAPS">G_TYPE_VALUE_ARRAY</a>
<a href="gobject-Generic-values.html#GValue">GValue</a>* <a href="gobject-Generic-values.html#g-value-init">g_value_init</a> (<a href="gobject-Generic-values.html#GValue">GValue</a> *value,
<a href="gobject-Type-Information.html#GType">GType</a> g_type);
void <a href="gobject-Generic-values.html#g-value-copy">g_value_copy</a> (const <a href="gobject-Generic-values.html#GValue">GValue</a> *src_value,
<a href="gobject-Generic-values.html#GValue">GValue</a> *dest_value);
<a href="gobject-Generic-values.html#GValue">GValue</a>* <a href="gobject-Generic-values.html#g-value-reset">g_value_reset</a> (<a href="gobject-Generic-values.html#GValue">GValue</a> *value);
void <a href="gobject-Generic-values.html#g-value-unset">g_value_unset</a> (<a href="gobject-Generic-values.html#GValue">GValue</a> *value);
<a
href="../glib/glib-Basic-Types.html#gboolean"
>gboolean</a> <a href="gobject-Generic-values.html#g-value-fits-pointer">g_value_fits_pointer</a> (const <a href="gobject-Generic-values.html#GValue">GValue</a> *value);
<a
href="../glib/glib-Basic-Types.html#gpointer"
>gpointer</a> <a href="gobject-Generic-values.html#g-value-peek-pointer">g_value_peek_pointer</a> (const <a href="gobject-Generic-values.html#GValue">GValue</a> *value);
<a
href="../glib/glib-Basic-Types.html#gboolean"
>gboolean</a> <a href="gobject-Generic-values.html#g-value-type-compatible">g_value_type_compatible</a> (<a href="gobject-Type-Information.html#GType">GType</a> src_type,
<a href="gobject-Type-Information.html#GType">GType</a> dest_type);
<a
href="../glib/glib-Basic-Types.html#gboolean"
>gboolean</a> <a href="gobject-Generic-values.html#g-value-type-transformable">g_value_type_transformable</a> (<a href="gobject-Type-Information.html#GType">GType</a> src_type,
<a href="gobject-Type-Information.html#GType">GType</a> dest_type);
<a
href="../glib/glib-Basic-Types.html#gboolean"
>gboolean</a> <a href="gobject-Generic-values.html#g-value-transform">g_value_transform</a> (const <a href="gobject-Generic-values.html#GValue">GValue</a> *src_value,
<a href="gobject-Generic-values.html#GValue">GValue</a> *dest_value);
void (<a href="gobject-Generic-values.html#GValueTransform">*GValueTransform</a>) (const <a href="gobject-Generic-values.html#GValue">GValue</a> *src_value,
<a href="gobject-Generic-values.html#GValue">GValue</a> *dest_value);
void <a href="gobject-Generic-values.html#g-value-register-transform-func">g_value_register_transform_func</a> (<a href="gobject-Type-Information.html#GType">GType</a> src_type,
<a href="gobject-Type-Information.html#GType">GType</a> dest_type,
<a href="gobject-Generic-values.html#GValueTransform">GValueTransform</a> transform_func);
<a
href="../glib/glib-Basic-Types.html#gchar"
>gchar</a>* <a href="gobject-Generic-values.html#g-strdup-value-contents">g_strdup_value_contents</a> (const <a href="gobject-Generic-values.html#GValue">GValue</a> *value);
</pre></div><div class="refsect1" lang="en"><a name="id2812129"></a><h2>Description</h2><p>
The <a href="gobject-Generic-values.html#GValue"><span class="type">GValue</span></a> structure is basically a variable container that consists
of a type identifier and a specific value of that type.
The type identifier within a <a href="gobject-Generic-values.html#GValue"><span class="type">GValue</span></a> structure always determines the
type of the associated value.
To create a undefined <a href="gobject-Generic-values.html#GValue"><span class="type">GValue</span></a> structure, simply create a zero-filled
<a href="gobject-Generic-values.html#GValue"><span class="type">GValue</span></a> structure. To initialize the <a href="gobject-Generic-values.html#GValue"><span class="type">GValue</span></a>, use the <a href="gobject-Generic-values.html#g-value-init"><tt class="function">g_value_init()</tt></a>
function. A <a href="gobject-Generic-values.html#GValue"><span class="type">GValue</span></a> cannot be used until it is initialized.
The basic type operations (such as freeing and copying) are determined
by the <a href="gobject-Type-Information.html#GTypeValueTable"><span class="type">GTypeValueTable</span></a> associated with the type ID stored in the <a href="gobject-Generic-values.html#GValue"><span class="type">GValue</span></a>.
Other <a href="gobject-Generic-values.html#GValue"><span class="type">GValue</span></a> operations (such as converting values between types) are
provided by this interface.
</p></div><div class="refsect1" lang="en"><a name="id2812231"></a><h2>Details</h2><div class="refsect2" lang="en"><a name="id2812236"></a><h3><a name="G-VALUE-HOLDS-CAPS"></a>G_VALUE_HOLDS()</h3><a class="indexterm" name="id2812247"></a><pre class="programlisting">#define G_VALUE_HOLDS(value,type) (G_TYPE_CHECK_VALUE_TYPE ((value), (type)))
</pre><p>
Returns <a
href="../glib/glib-Standard-Macros.html#TRUE-CAPS"
><span class="type">TRUE</span></a> if <i class="parameter"><tt>value</tt></i> holds (or contains) a value of <i class="parameter"><tt>type</tt></i>.
This macro will also check for <i class="parameter"><tt>value</tt></i> != <a
href="../glib/glib-Standard-Macros.html#NULL-CAPS"
><span class="type">NULL</span></a> and issue a
warning if the check fails.
</p><div class="variablelist"><table border="0"><col align="left" valign="top"><tbody><tr><td><span class="term"><i class="parameter"><tt>value</tt></i> :</span></td><td>
</td></tr><tr><td><span class="term"><i class="parameter"><tt>type</tt></i> :</span></td><td>
</td></tr></tbody></table></div></div><hr><div class="refsect2" lang="en"><a name="id2812332"></a><h3><a name="G-VALUE-TYPE-CAPS"></a>G_VALUE_TYPE()</h3><a class="indexterm" name="id2812343"></a><pre class="programlisting">#define G_VALUE_TYPE(value) (((GValue*) (value))->g_type)
</pre><p>
Returns the type identifier of <i class="parameter"><tt>value</tt></i>.
</p><div class="variablelist"><table border="0"><col align="left" valign="top"><tbody><tr><td><span class="term"><i class="parameter"><tt>value</tt></i> :</span></td><td>A <a href="gobject-Generic-values.html#GValue"><span class="type">GValue</span></a> structure.
</td></tr></tbody></table></div></div><hr><div class="refsect2" lang="en"><a name="id2812392"></a><h3><a name="G-VALUE-TYPE-NAME-CAPS"></a>G_VALUE_TYPE_NAME()</h3><a class="indexterm" name="id2812403"></a><pre class="programlisting">#define G_VALUE_TYPE_NAME(value) (g_type_name (G_VALUE_TYPE (value)))
</pre><p>
Returns the type name of <i class="parameter"><tt>value</tt></i>.
</p><div class="variablelist"><table border="0"><col align="left" valign="top"><tbody><tr><td><span class="term"><i class="parameter"><tt>value</tt></i> :</span></td><td>A <a href="gobject-Generic-values.html#GValue"><span class="type">GValue</span></a> structure.
</td></tr></tbody></table></div></div><hr><div class="refsect2" lang="en"><a name="id2812451"></a><h3><a name="G-TYPE-IS-VALUE-CAPS"></a>G_TYPE_IS_VALUE()</h3><a class="indexterm" name="id2812462"></a><pre class="programlisting">#define G_TYPE_IS_VALUE(type) (g_type_check_is_value_type (type))
</pre><p>
Return whether the passed in type ID can be used for <a href="gobject-Generic-values.html#g-value-init"><tt class="function">g_value_init()</tt></a>.
That is, this macro checks whether this type provides an implementation
of the <a href="gobject-Type-Information.html#GTypeValueTable"><span class="type">GTypeValueTable</span></a> functions required for a type to create a <a href="gobject-Generic-values.html#GValue"><span class="type">GValue</span></a> of.
</p><div class="variablelist"><table border="0"><col align="left" valign="top"><tbody><tr><td><span class="term"><i class="parameter"><tt>type</tt></i> :</span></td><td> A <a href="gobject-Type-Information.html#GType"><span class="type">GType</span></a> value.
</td></tr><tr><td><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></td><td>Whether <i class="parameter"><tt>type</tt></i> is suitable as a <a href="gobject-Generic-values.html#GValue"><span class="type">GValue</span></a> type.
</td></tr></tbody></table></div></div><hr><div class="refsect2" lang="en"><a name="id2812559"></a><h3><a name="G-TYPE-IS-VALUE-ABSTRACT-CAPS"></a>G_TYPE_IS_VALUE_ABSTRACT()</h3><a class="indexterm" name="id2812570"></a><pre class="programlisting">#define G_TYPE_IS_VALUE_ABSTRACT(type) (g_type_test_flags ((type), G_TYPE_FLAG_VALUE_ABSTRACT))
</pre><p>
Returns <tt class="literal">TRUE</tt> if <i class="parameter"><tt>type</tt></i> is an abstract value type. An abstract value type
introduces a value table, but can't be used for <a href="gobject-Generic-values.html#g-value-init"><tt class="function">g_value_init()</tt></a> and is normally
used as an abstract base type for derived value types.
</p><div class="variablelist"><table border="0"><col align="left" valign="top"><tbody><tr><td><span class="term"><i class="parameter"><tt>type</tt></i> :</span></td><td>A <a href="gobject-Type-Information.html#GType"><span class="type">GType</span></a> value.
</td></tr></tbody></table></div></div><hr><div class="refsect2" lang="en"><a name="id2812638"></a><h3><a name="G-IS-VALUE-CAPS"></a>G_IS_VALUE()</h3><a class="indexterm" name="id2812649"></a><pre class="programlisting">#define G_IS_VALUE(value) (G_TYPE_CHECK_VALUE (value))
</pre><p>
Returns <a
href="../glib/glib-Standard-Macros.html#TRUE-CAPS"
><span class="type">TRUE</span></a> if <i class="parameter"><tt>value</tt></i> is a valid and initialized <a href="gobject-Generic-values.html#GValue"><span class="type">GValue</span></a> structure.
</p><div class="variablelist"><table border="0"><col align="left" valign="top"><tbody><tr><td><span class="term"><i class="parameter"><tt>value</tt></i> :</span></td><td>A <a href="gobject-Generic-values.html#GValue"><span class="type">GValue</span></a> structure.
</td></tr></tbody></table></div></div><hr><div class="refsect2" lang="en"><a name="id2812713"></a><h3><a name="GValue"></a>struct GValue</h3><a class="indexterm" name="id2812724"></a><pre class="programlisting">struct GValue {
};
</pre><p>
An opaque structure used to hold different types of values.
The data within the structure has protected scope: it is accessible only
to functions within a <a href="gobject-Type-Information.html#GTypeValueTable"><span class="type">GTypeValueTable</span></a> structure, or implementations of
the g_value_*() API. That is, code portions which implement new fundamental
types.
<a href="gobject-Generic-values.html#GValue"><span class="type">GValue</span></a> users can not make any assumptions about how data is stored
within the 2 element <a href="gobject-Generic-values.html#GValue"><span class="type">GValue</span></a>.data[] union, and the g_type member should
only be accessed through the <a href="gobject-Generic-values.html#G-VALUE-TYPE-CAPS"><tt class="function">G_VALUE_TYPE()</tt></a> macro.
</p></div><hr><div class="refsect2" lang="en"><a name="id2812780"></a><h3><a name="G-TYPE-VALUE-CAPS"></a>G_TYPE_VALUE</h3><a class="indexterm" name="id2812792"></a><pre class="programlisting">#define G_TYPE_VALUE (g_value_get_type ())
</pre><p>
Returns the type ID of the "GValue" type which is a boxed type,
used to pass around pointers to GValues.
</p></div><hr><div class="refsect2" lang="en"><a name="id2812809"></a><h3><a name="G-TYPE-VALUE-ARRAY-CAPS"></a>G_TYPE_VALUE_ARRAY</h3><a class="indexterm" name="id2812820"></a><pre class="programlisting">#define G_TYPE_VALUE_ARRAY (g_value_array_get_type ())
</pre><p>
Returns the type ID of the "GValueArray" type which is a boxed type,
used to pass around pointers to GValueArrays.
</p></div><hr><div class="refsect2" lang="en"><a name="id2812838"></a><h3><a name="g-value-init"></a>g_value_init ()</h3><a class="indexterm" name="id2812848"></a><pre class="programlisting"><a href="gobject-Generic-values.html#GValue">GValue</a>* g_value_init (<a href="gobject-Generic-values.html#GValue">GValue</a> *value,
<a href="gobject-Type-Information.html#GType">GType</a> g_type);</pre><p>
Initializes <i class="parameter"><tt>value</tt></i> with the default value of <i class="parameter"><tt>type</tt></i>.
</p><div class="variablelist"><table border="0"><col align="left" valign="top"><tbody><tr><td><span class="term"><i class="parameter"><tt>value</tt></i> :</span></td><td> A zero-filled (uninitialized) <a href="gobject-Generic-values.html#GValue"><span class="type">GValue</span></a> structure.
</td></tr><tr><td><span class="term"><i class="parameter"><tt>g_type</tt></i> :</span></td><td> Type the <a href="gobject-Generic-values.html#GValue"><span class="type">GValue</span></a> should hold values of.
</td></tr><tr><td><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></td><td>
</td></tr></tbody></table></div></div><hr><div class="refsect2" lang="en"><a name="id2812955"></a><h3><a name="g-value-copy"></a>g_value_copy ()</h3><a class="indexterm" name="id2812966"></a><pre class="programlisting">void g_value_copy (const <a href="gobject-Generic-values.html#GValue">GValue</a> *src_value,
<a href="gobject-Generic-values.html#GValue">GValue</a> *dest_value);</pre><p>
Copies the value of <i class="parameter"><tt>src_value</tt></i> into <i class="parameter"><tt>dest_value</tt></i>.
</p><div class="variablelist"><table border="0"><col align="left" valign="top"><tbody><tr><td><span class="term"><i class="parameter"><tt>src_value</tt></i> :</span></td><td> An initialized <a href="gobject-Generic-values.html#GValue"><span class="type">GValue</span></a> structure.
</td></tr><tr><td><span class="term"><i class="parameter"><tt>dest_value</tt></i> :</span></td><td> An initialized <a href="gobject-Generic-values.html#GValue"><span class="type">GValue</span></a> structure of the same type as <i class="parameter"><tt>src_value</tt></i>.
</td></tr></tbody></table></div></div><hr><div class="refsect2" lang="en"><a name="id2813068"></a><h3><a name="g-value-reset"></a>g_value_reset ()</h3><a class="indexterm" name="id2813080"></a><pre class="programlisting"><a href="gobject-Generic-values.html#GValue">GValue</a>* g_value_reset (<a href="gobject-Generic-values.html#GValue">GValue</a> *value);</pre><p>
Clears the current value in <i class="parameter"><tt>value</tt></i> and resets it to the default value
(as if the value had just been initialized).
</p><div class="variablelist"><table border="0"><col align="left" valign="top"><tbody><tr><td><span class="term"><i class="parameter"><tt>value</tt></i> :</span></td><td> An initialized <a href="gobject-Generic-values.html#GValue"><span class="type">GValue</span></a> structure.
</td></tr><tr><td><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></td><td>
</td></tr></tbody></table></div></div><hr><div class="refsect2" lang="en"><a name="id2813152"></a><h3><a name="g-value-unset"></a>g_value_unset ()</h3><a class="indexterm" name="id2813163"></a><pre class="programlisting">void g_value_unset (<a href="gobject-Generic-values.html#GValue">GValue</a> *value);</pre><p>
Clears the current value in <i class="parameter"><tt>value</tt></i> and "unsets" the type,
this releases all resources associated with this GValue.
An unset value is the same as an uninitialized (zero-filled)
<a href="gobject-Generic-values.html#GValue"><span class="type">GValue</span></a> structure.
</p><div class="variablelist"><table border="0"><col align="left" valign="top"><tbody><tr><td><span class="term"><i class="parameter"><tt>value</tt></i> :</span></td><td> An initialized <a href="gobject-Generic-values.html#GValue"><span class="type">GValue</span></a> structure.
</td></tr></tbody></table></div></div><hr><div class="refsect2" lang="en"><a name="id2813234"></a><h3><a name="g-value-fits-pointer"></a>g_value_fits_pointer ()</h3><a class="indexterm" name="id2813246"></a><pre class="programlisting"><a
href="../glib/glib-Basic-Types.html#gboolean"
>gboolean</a> g_value_fits_pointer (const <a href="gobject-Generic-values.html#GValue">GValue</a> *value);</pre><p>
Determines if <i class="parameter"><tt>value</tt></i> will fit inside the size of a pointer value.
This is an internal function introduced mainly for C marshallers.
</p><div class="variablelist"><table border="0"><col align="left" valign="top"><tbody><tr><td><span class="term"><i class="parameter"><tt>value</tt></i> :</span></td><td> An initialized <a href="gobject-Generic-values.html#GValue"><span class="type">GValue</span></a> structure.
</td></tr><tr><td><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></td><td> <a
href="../glib/glib-Standard-Macros.html#TRUE-CAPS"
><span class="type">TRUE</span></a> if <i class="parameter"><tt>value</tt></i> will fit inside a pointer value.
</td></tr></tbody></table></div></div><hr><div class="refsect2" lang="en"><a name="id2813333"></a><h3><a name="g-value-peek-pointer"></a>g_value_peek_pointer ()</h3><a class="indexterm" name="id2813344"></a><pre class="programlisting"><a
href="../glib/glib-Basic-Types.html#gpointer"
>gpointer</a> g_value_peek_pointer (const <a href="gobject-Generic-values.html#GValue">GValue</a> *value);</pre><p>
Return the value contents as pointer. This function asserts that
<a href="gobject-Generic-values.html#g-value-fits-pointer"><tt class="function">g_value_fits_pointer()</tt></a> returned <a
href="../glib/glib-Standard-Macros.html#TRUE-CAPS"
><span class="type">TRUE</span></a> for the passed in value.
This is an internal function introduced mainly for C marshallers.
</p><div class="variablelist"><table border="0"><col align="left" valign="top"><tbody><tr><td><span class="term"><i class="parameter"><tt>value</tt></i> :</span></td><td> An initialized <a href="gobject-Generic-values.html#GValue"><span class="type">GValue</span></a> structure.
</td></tr><tr><td><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></td><td> <a
href="../glib/glib-Standard-Macros.html#TRUE-CAPS"
><span class="type">TRUE</span></a> if <i class="parameter"><tt>value</tt></i> will fit inside a pointer value.
</td></tr></tbody></table></div></div><hr><div class="refsect2" lang="en"><a name="id2813445"></a><h3><a name="g-value-type-compatible"></a>g_value_type_compatible ()</h3><a class="indexterm" name="id2813457"></a><pre class="programlisting"><a
href="../glib/glib-Basic-Types.html#gboolean"
>gboolean</a> g_value_type_compatible (<a href="gobject-Type-Information.html#GType">GType</a> src_type,
<a href="gobject-Type-Information.html#GType">GType</a> dest_type);</pre><p>
Returns whether a <a href="gobject-Generic-values.html#GValue"><span class="type">GValue</span></a> of type <i class="parameter"><tt>src_type</tt></i> can be copied into
a <a href="gobject-Generic-values.html#GValue"><span class="type">GValue</span></a> of type <i class="parameter"><tt>dest_type</tt></i>.
</p><div class="variablelist"><table border="0"><col align="left" valign="top"><tbody><tr><td><span class="term"><i class="parameter"><tt>src_type</tt></i> :</span></td><td> source type to be copied.
</td></tr><tr><td><span class="term"><i class="parameter"><tt>dest_type</tt></i> :</span></td><td>destination type for copying.
</td></tr><tr><td><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></td><td> <tt class="literal">TRUE</tt> if <a href="gobject-Generic-values.html#g-value-copy"><tt class="function">g_value_copy()</tt></a> is possible with <i class="parameter"><tt>src_type</tt></i> and <i class="parameter"><tt>dest_type</tt></i>.
</td></tr></tbody></table></div></div><hr><div class="refsect2" lang="en"><a name="id2813592"></a><h3><a name="g-value-type-transformable"></a>g_value_type_transformable ()</h3><a class="indexterm" name="id2813605"></a><pre class="programlisting"><a
href="../glib/glib-Basic-Types.html#gboolean"
>gboolean</a> g_value_type_transformable (<a href="gobject-Type-Information.html#GType">GType</a> src_type,
<a href="gobject-Type-Information.html#GType">GType</a> dest_type);</pre><p>
Check whether <a href="gobject-Generic-values.html#g-value-transform"><tt class="function">g_value_transform()</tt></a> is able to transform values
of type <i class="parameter"><tt>src_type</tt></i> into values of type <i class="parameter"><tt>dest_type</tt></i>.
</p><div class="variablelist"><table border="0"><col align="left" valign="top"><tbody><tr><td><span class="term"><i class="parameter"><tt>src_type</tt></i> :</span></td><td> Source type.
</td></tr><tr><td><span class="term"><i class="parameter"><tt>dest_type</tt></i> :</span></td><td>Target type.
</td></tr><tr><td><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></td><td> <tt class="literal">TRUE</tt> if the transformation is possible, <tt class="literal">FALSE</tt> otherwise.
</td></tr></tbody></table></div></div><hr><div class="refsect2" lang="en"><a name="id2813718"></a><h3><a name="g-value-transform"></a>g_value_transform ()</h3><a class="indexterm" name="id2813730"></a><pre class="programlisting"><a
href="../glib/glib-Basic-Types.html#gboolean"
>gboolean</a> g_value_transform (const <a href="gobject-Generic-values.html#GValue">GValue</a> *src_value,
<a href="gobject-Generic-values.html#GValue">GValue</a> *dest_value);</pre><p>
Tries to cast the contents of <i class="parameter"><tt>src_value</tt></i> into a type apropriate
to store in <i class="parameter"><tt>dest_value</tt></i>, e.g. to transform a <tt class="literal">G_TYPE_INT</tt> value
into a <tt class="literal">G_TYPE_FLOAT</tt> value. Performing transformations between
value types might incour precision lossage. Especially
transformations into strings might reveal seemingly arbitrary
results and shouldn't be relied upon for production code (such
as rcfile value or object property serialization).
</p><div class="variablelist"><table border="0"><col align="left" valign="top"><tbody><tr><td><span class="term"><i class="parameter"><tt>src_value</tt></i> :</span></td><td> Source value.
</td></tr><tr><td><span class="term"><i class="parameter"><tt>dest_value</tt></i> :</span></td><td>Target value.
</td></tr><tr><td><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></td><td> Whether a transformation rule was found and could be applied.
Upon failing transformations, <i class="parameter"><tt>dest_value</tt></i> is left untouched.
</td></tr></tbody></table></div></div><hr><div class="refsect2" lang="en"><a name="id2813846"></a><h3><a name="GValueTransform"></a>GValueTransform ()</h3><a class="indexterm" name="id2813857"></a><pre class="programlisting">void (*GValueTransform) (const <a href="gobject-Generic-values.html#GValue">GValue</a> *src_value,
<a href="gobject-Generic-values.html#GValue">GValue</a> *dest_value);</pre><p>
The type of value transformation functions which can be registered with
<a href="gobject-Generic-values.html#g-value-register-transform-func"><tt class="function">g_value_register_transform_func()</tt></a>.
</p><div class="variablelist"><table border="0"><col align="left" valign="top"><tbody><tr><td><span class="term"><i class="parameter"><tt>src_value</tt></i> :</span></td><td> Source value.
</td></tr><tr><td><span class="term"><i class="parameter"><tt>dest_value</tt></i> :</span></td><td>Target value.
</td></tr></tbody></table></div></div><hr><div class="refsect2" lang="en"><a name="id2813938"></a><h3><a name="g-value-register-transform-func"></a>g_value_register_transform_func ()</h3><a class="indexterm" name="id2813949"></a><pre class="programlisting">void g_value_register_transform_func (<a href="gobject-Type-Information.html#GType">GType</a> src_type,
<a href="gobject-Type-Information.html#GType">GType</a> dest_type,
<a href="gobject-Generic-values.html#GValueTransform">GValueTransform</a> transform_func);</pre><p>
Registers a value transformation function for use in <a href="gobject-Generic-values.html#g-value-transform"><tt class="function">g_value_transform()</tt></a>.
A previously registered transformation function for <i class="parameter"><tt>src_type</tt></i> and <i class="parameter"><tt>dest_type</tt></i>
will be replaced.
</p><div class="variablelist"><table border="0"><col align="left" valign="top"><tbody><tr><td><span class="term"><i class="parameter"><tt>src_type</tt></i> :</span></td><td> Source type.
</td></tr><tr><td><span class="term"><i class="parameter"><tt>dest_type</tt></i> :</span></td><td>Target type.
</td></tr><tr><td><span class="term"><i class="parameter"><tt>transform_func</tt></i> :</span></td><td>a function which transforms values of type <i class="parameter"><tt>src_type</tt></i>
into value of type <i class="parameter"><tt>dest_type</tt></i>
</td></tr></tbody></table></div></div><hr><div class="refsect2" lang="en"><a name="id2814077"></a><h3><a name="g-strdup-value-contents"></a>g_strdup_value_contents ()</h3><a class="indexterm" name="id2814088"></a><pre class="programlisting"><a
href="../glib/glib-Basic-Types.html#gchar"
>gchar</a>* g_strdup_value_contents (const <a href="gobject-Generic-values.html#GValue">GValue</a> *value);</pre><p>
Return a newly allocated string, which describes the contents of a <a href="gobject-Generic-values.html#GValue"><span class="type">GValue</span></a>.
The main purpose of this function is to describe <a href="gobject-Generic-values.html#GValue"><span class="type">GValue</span></a> contents for debugging
output, the way in which the contents are described may change between different
GLib versions.
</p><div class="variablelist"><table border="0"><col align="left" valign="top"><tbody><tr><td><span class="term"><i class="parameter"><tt>value</tt></i> :</span></td><td> <a href="gobject-Generic-values.html#GValue"><span class="type">GValue</span></a> which contents are to be described.
</td></tr><tr><td><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></td><td>Newly allocated string.
</td></tr></tbody></table></div></div></div><div class="refsect1" lang="en"><a name="id2814174"></a><h2>See Also</h2><p>
The fundamental types which all support <a href="gobject-Generic-values.html#GValue"><span class="type">GValue</span></a> operations and thus
can be used as a type initializer for <a href="gobject-Generic-values.html#g-value-init"><tt class="function">g_value_init()</tt></a> are defined by
a separate interface. See the Standard Values API for details.
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